Customarily, moving body motion detection systems, notably for automobile or aerial radar systems, utilize the Doppler effect to determine the speed of displacement of a moving body. Radar systems comprise an emitter of a radiofrequency signal and a receiver of the radiofrequency signal. Once the signal has been emitted by the emitter towards the moving body in motion the latter is reflected and then sensed by the receiver. The determination of the speed of the moving body is based on the fact that the frequency of the sensed signal varies as a function of the radial speed with respect to the carrier. In a Galilean referential frame, the referential frame of the medium in which the wave propagates (for example the atmosphere for radars), if by convention the speeds are considered positive in the direction of propagation of the emitted signal, the frequency emitted by the emitter is denoted by Femitter and the frequency received by the receiver by Freceiver, we obtain:Freceiver=(C−Vreceiver)/(C−Vemitter)*Femitter i.e. Fdoppler=(Vreceiver−Vemitter)/C*Femitter With:Fdoppler=Femitter−Freceiver 
Vemitter, the radial speed of the emitter, Vreceiver, the radial speed of the receiver, and C the speed of light.
When the emitter is situated on the moving body, direct measurement of the relative speed of a moving body on a single frequency is not possible since it requires two oscillators which are perfectly phase-coherent, one at the level of the emitter and the other at the level of the receiver. This measurement would also require a perfectly constant and known frequency gap between the oscillator of the emitter and the oscillator of the receiver.
The measurement of the speed of a moving body is a significant point in servocontrol. The mechanical stresses introduced by the vibrations and knocks of the moving bodies on the stability of the frequencies of the beacons with which they are equipped are significant, thus raising the cost of the onboard electronics or indeed prohibiting the employment of this solution on inexpensive applications. Thus, a problem with the prior art solutions resides in the difficulty of controlling the stability and purity of the wave emitted as a function of the environment (temperature, vibrations, power supply modulation etc.).
According to the prior art, there exist various ways of calculating the azimuthal and elevational angular positions. In the case of an aircraft comprising an optronics pod equipped with antennas, it is possible to ascertain these data on the basis of goniometric weighings and interferometers. Goniometric weighings lack precision and require precise calibrations, while interferometers are expensive and implement complicated electronics.
It is also possible to install a radar in proximity to the departure of the moving body so as to perform the measurements with the known problems of discretion and jamming, the radar being by necessity pointed towards the objective.